Napoleon c



UNITED STATES PATENT OFFICEQ/ NAPOLEON O. HUBBELL, OF HARTFORD,CONNECTICUT, ASSIGNOR TO LOUIS F. HEUBLEIN, OF SAME PLACE.

PROCESS OF HARDl-ZNING STEEL.

EPECIFIUATEQN forming part of Letters Patent No, 310,433, dated January6, 1885.

Application filed April 2 1884. (No specimens.)

To all whom, it may concern:

Be it known that I, NAPOLEON C. HUBBELL, of Hartford, in the'county ofHartford and State of Connecticut, have invented a new Im- 5 provementin the Process of Hardening Steel; and 1 do hereby declare the followingto be a full,- clear, and exact description of the same.

This invention relates to an in'iprovemeut in the process of hardeningsteel. The usual method of hardening steel is to heat it to a highdegree, then plunge it into cold water. It is to this method ofhardening that my invention particularly relates. Cold-water hardeningcannot be employed with any degree of satisfaction in the lower gradesof steel, and, owing to the high degree of heat necessary in the highergrades, the steel is frequently cracked on its immersion into the coldwater. For tools and like purposes only the higher '20 grade of steelcan be employed, and a serious difficulty in such tools arises from thecracking before mentioned during .the process of hardening.

The object of my invention is to avoid the high degree of heat usuallyemployed in hardening, as well as to enable the use of lower grades ofsteel; and my invention consists in hardening the heated steel in a bathcomposed of shell-marl and water in the proportions substantially ashereinafter described.

I take what is commonly known as shellmarl as it comes from the bed, andpreferably reduce it to a powder. Of this powder I take in theproportion of about three and one- 3 5 half pounds to ten gallons ofwater, and thoroughly mix it with the water, which mixture forms thebath for-hardening. The steel to be hardened is heated in the usualmanner, but to a much lower degree than in tempering in cold water. Itis then plunged into the marl 4o bath in the usual manner of introducinginto the water bath until 0001. The action of the combined marl andwater upon the steel is to produce the same degree of hardness by a muchlower degree of heat, and because of this lower 5 heat the cracking asexperienced in dies, tools, &c., is entirely avoided. Again, it is foundby actual use that the lower grades of steel, even to the lowest, may behardened in my improved bath and employed for dies, tools, &c., withequal success to the finer grades of steel. In fact, the lower grades ofsteel hardened under my improved process are more durable and lessliable to break than the best steel hardened by cold water alone, andwith out possibility of cracking in the process of hardening.

Vhile my improved process is speciallyadapted to hardening tools, dies,&c., equally beneficial results attend its use in hardening steel forother purposes.

lt will be understood that after hardeningthe temper is drawn in theusual manner.

The proportions of marl to water may be varied to a considerable extent;butI find that the proportions of marl to the water above named is aboutwhat the water will take up.

I claim- The herein-described improvement in the process of hardeningsteel, consisting in immersing the hot steel in a bath composed of waterand shell marl, substantially as described.

NAPOLEON C. HUBBELL.

W i tn csses G. Invruc BLAKE, TARIL HEISSMA NN.

